A New Horatia spp. from the Balkans (Gastropoda: Hydrobiidae Stimpson, 1865)

In this article we describe a new species of Horatia from North Macedonia (former FYROM). Description of the new species is based on the shell characters only. This new species is compared with the other known species of Horatia from the Balkans, i.e., H. klecakiana, H. novoselensis and H. macedonica


Introduction
The genus Horatia Bourguignat 1887 is characterized by the peristome which is at the columella straight and thickened. The type species Horatia klecakiana Bourguignat 1877 has been described as a very small species (H = 0.5 mm, D = 1.0 mm) with a wide and deep umbilicus (Bourguignat 1887, p. 49). In addition to Horatia klecakiana, with its type locality in the source of Cetina river in Dalmatia, Bourguignat described in 1887 eight more Horatia spp. from this locality and most of these species should also occur in Albania. Brusina (1904) thought that the description of these many species is untenable. Binder (1957) studied Horatia klecakiana from type locality and found an enormous variability of the shells, obviously ignored by Bourguignat. Later Ant (1962) depicted Horatia klecakiana from the Ombla spring in Croatia (leg. Schütt) which has nothing in common with the original description, too large, no umbilicus and having a circular aperture. The Horatia from the Ombla spring has been described by Schütt (1961) as Horatia knorri, which has not been accepted by Ant (1962) as a distinct species. Horatia klecakiana has been misinterpreted also in several publications which deal with molecular-genetics. For the first time Wilke et al. (2001), who worked with samples outside the type locality (spring of the Vrana River, between Vrana and Radosinovci in Croatia, Szarowska & Falniowski leg. and det.), which turned out to group sister with Radomaniola, thus obviously misidentified. This sequence has been published in GenBank and has been used in some other publications too. Szarowska (2006) defined Horatia as a genus with a wide umbilicus and, in lateral profile, a simple outer lip abapically sinuated, while Bodon et al, (2001) decribed the umbilicus as not very wide. Later Szarowska & Falniowski (2014) studied "Horatia klecakiana" from the type locality, to show that it is not close to Radomaniola. However, the species used in their work had a closed umbilicus, the border of the aperture at the columella is not straight, and the shell is much larger than Horatia klecakiana. It looks more similar to Sadleriana, a genus to which it groups sister in their molecular-genetic tree. Thus the phylogenetic position of Horatia remains still unknow. Radoman (1966) depicted a drawing of Horatia klecakiana from the region of the source of the river Cetina which showed the characteristic features of the species but it is somewhat larger.
Considering Bank et al. (2017) other accepted Horatia spp. are H. macedonica (Kuščer, 1937) (type locality: big spring west of Skopje, North Macedonia, and H. novoselensis Radoman, 1966 (type locality: Novo Selo, North Macedonia). This paper is intended to contribute to the knowledge of the genus Horatia and to describe a new species from North Macedonia.

Material and methods
The snails have been collected by Robert Reuselaars by hand during a fieldtrip in 2014 in North Macedonia. To evaluate the collected samples we reviewed the collected material with the known species of Horatia from the Balkans.
The measurements of the shells were carried out using a stereo microscope (ZEISS) with an eyepiece micrometer; the photographs were made with a digital camera system (Leica R8). The type material is stored in RMNH (Rijskmuseum van Natuurlijke Historie Naturalis in Leiden, The Netherlands) and in the collections of Peter Glöer and Robert Reuselaars.

Taxonomic part
Family Hydrobiidae Stimpson, 1865 Genus Horatia Bourguignat, 1887 Type species: Horatia klecakiana Bourguignat 1887 Description: Shell valvatoid, conical to globular with a prominent body whorl. The umbilicus is wide and deep or slightly covered by the last whorl. The peristome is at the columella straight, broadened or reflexed. The outer lip of the circular aperture is oblique, its lower end drawn backwards from lateral view.

Differentiating charcters:
The shell shape of some Sadleriana spp. are looking similar, but the latter genus has no umbilicus and the peristome is in the region of the columella broader. Habitat: Type locality: natural spring (appr. 2 m 2 ), the specimen were collected from small stones from the bottom of the basin; secondary sampling site: artificial basin (apr. 0.5 m 2 ) were the specimen were collected from the concrete sides of the basin.
Etymology: Named after the nearby town Podvis. Description: The shell is conical to globular with 3-3.5 slightly convex whorls with a deep suture. The body whorl is prominent, the spire is short with slightly shouldered, convex whorls. The aperture is nearly circular. The peristome is sharp straight and somewhat thickened at the columella. The umbilicus is open and slightly covered by the last whorl. The ratio of shell height to shell width is 0.8-1.0. The shell is 0.85-1.55 mm high and 1.05-1.6 mm broad. Differentiating characters: In Horatia klecakiana and H. novoselensis the umbilicus is much wider than in H. podvisensis n. sp. In Horatia macedonica the tangentline of the spire is straight and the whorls are not convex. The aperture of Horatia macedonica is angled at the top and not rounded as it is in H. podvisensis n. sp. In addition the umbilicus in H.podvisensis n. sp. is covered by the last whorl that in adult shells the umbilicus is only very narrow visible ( fig. 5). Moreover, Horatia macedonica is larger (H=1.4-1.6 mm, D=1.6-1.8 mm) than H. podvisensis (H=0.9-1.6 mm and D=1.0-1.6 mm).
Distribution: Western part of North Macedonia; only known from this region. Conservation: We do not consider Horatia podvisensis n. sp. as an endangered species because it lives in two localities and there is lesser chance of human disturbance, especially in the type locality. Because of the separated localities of which one is quit remote, we assume it can be found in other (remote) springs in the area.